Non-contact electric power transmission system, charging station, and vehicle

ABSTRACT

A charging station includes a plurality of electric power transmission portions and a power supply ECU. When a second vehicle is parked at a position where it can receive electric power from a first electric power transmission portion and when the second vehicle receives weak electric power from the first electric power transmission portion, the second vehicle transmits to the power supply ECU, an occupation signal which allows determination that the parking position corresponds to the first electric power transmission portion. When the power supply ECU receives the occupation signal of the first electric power transmission portion from the second vehicle, the power supply ECU stops transmission of weak electric power from the first electric power transmission portion and guides a first vehicle to a second electric power transmission portion.

This nonprovisional application is based on Japanese Patent ApplicationNo. 2014-017139 filed with the Japan Patent Office on Jan. 31, 2014, theentire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1 Field of the Invention

The present invention relates to a non-contact electric powertransmission system, a charging station, and a vehicle.

2. Description of the Background Art

Japanese Patent Laying-Open No. 2013-135572 discloses a non-contactcharging system in which electric power is transmitted from a vehicle toa charging station in a non-contact manner. In the non-contact chargingsystem, positioning between an electric power transmission portion ofthe charging station and an electric power reception portion of thevehicle is carried out in order to enhance efficiency in electric powertransmission and reception.

In the publication above, one control unit on an electric powertransmission side is provided in a charging station and this controlunit on the electric power transmission side controls one electric powertransmission portion (an electric power transmission coil).

Such a type that one control unit controls a plurality of electric powertransmission portions, however, is possible as a type of the chargingstation.

Here, in such a situation that vehicles are parked at some electricpower transmission portions of a plurality of electric powertransmission portions, it is possible that a new vehicle enters thecharging station for Charging. When the electric power transmissionportions are supplying electric power to already stopped vehicles, thecharging station can determine that the vehicles are present at thoseelectric power transmission portions. On the other hand, it is alsopossible that in spite of completion of charging of the vehicles, thevehicles remain stopped over the electric power transmission portionswithout moving. In such a state, the charging station cannot knowwhether or not the vehicles remain stopped at the electric powertransmission portions.

Consequently, the charging station cannot determine to which electricpower transmission portion a vehicle which has newly entered thecharging station should be guided.

If a sensor for checking a position of a vehicle is to be provided foreach parking frame, cost for installation of a charging stationincreases and construction also requires efforts.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a non-contact electricpower transmission system which can guide a vehicle which has newlyarrived at a charging station to an empty electric power transmissionportion, a charging station, and a vehicle.

In summary, this invention is directed to a non-contact electric powertransmission system including first and second vehicles and a chargingstation. The charging station includes a plurality of electric powertransmission portions which can transmit electric power to the vehiclesin a non-contact manner and an electric power transmission control unitcontrolling electric power transmission from the plurality of electricpower transmission portions. The electric power transmission controlunit has a first electric power transmission portion, which is nottransmitting electric power, of the plurality of electric powertransmission portions transmit weak electric power when the electricpower transmission control unit receives a signal requesting electricpower transmission from the first vehicle. The second vehicle transmitsto the electric power transmission control unit, an occupation signalwhich allows determination that a parking position corresponds to thefirst electric power transmission portion when the second vehicle isparked at a position where the second vehicle can receive electric powerfrom the first electric power transmission portion and when the secondvehicle receives weak electric power from the first electric powertransmission portion. The electric power transmission control unitguides the first vehicle to an electric power transmission portion otherthan the first electric power transmission portion when the electricpower transmission control unit receives the occupation signal from thesecond vehicle.

According to the configuration above, for example, even when the secondvehicle remains stopped without moving after charging by the firstelectric power transmission portion, the charging station is notified ofthe fact that the second vehicle is occupying the first electric powertransmission portion. Therefore, the charging station can guide thefirst vehicle, which has sent a signal requesting electric powertransmission, to an electric power transmission portion other than thefirst electric power transmission portion.

Preferably, the electric power transmission control unit allows electricpower transmission with electric power characteristics of weak electricpower from the plurality of electric power transmission portions beingdiffered for each electric power transmission portion, and the secondvehicle transmits to the electric power transmission control unit, theoccupation signal in accordance with the electric power characteristicsof received weak electric power.

With such a configuration, the second vehicle can know based on electricpower characteristics of the received weak electric power, what kind ofelectric power transmission portion the electric power transmissionportion where the second vehicle is stopped is. Then, the second vehiclecan return information which allows determination of an electric powertransmission portion to the charging station.

More preferably, the electric power characteristics differed for eachelectric power transmission portion are a time period for supply of theweak electric power, and the second vehicle transmits a signalindicating the time period for supply as the occupation signal.

More preferably, the electric power characteristics differed for eachelectric power transmission portion are the number of times of switchingbetween on and off of the weak electric power, and the second vehicletransmits a signal indicating the number of times of switching as theoccupation signal.

Preferably, the second vehicle holds information indicating that theelectric power transmission portion used for charging is the firstelectric power transmission portion of the plurality of electric powertransmission portions, also after end of charging. The second vehicletransmits the occupation signal based on the held information when thesecond vehicle receives the weak electric power while the second vehicleis parked at the position corresponding to the first electric powertransmission portion after end of charging.

According to the configuration above, without such processing asdiffering electric power characteristics for each electric powertransmission portion at the time of transmission of weak electric power,the second vehicle can transmit an occupation signal.

Preferably, the second vehicle includes an electric power receptiondevice which can receive electric power from any of the plurality ofelectric power transmission portions, a power storage device, a chargingrelay provided between the electric power reception device and the powerstorage device, a distance sensing portion, and an electric powerreception control unit controlling the charging relay and the distancesensing portion. The distance sensing portion has a resistor and adistance sensing relay with which the resistor is connected between apair of output lines of the electric power reception device. Theelectric power reception control unit renders the charging relayconductive, and renders the distance sensing relay non-conductive whenthe power storage device is charged, and renders the charging relaynon-conductive and renders the distance sensing relay conductive aftercharging of the power storage device is completed.

With the configuration above, reception of weak electric power by thevehicle can be separate from charging of the power storage device and adistance can suitably be sensed based on a received voltage generated bythe weak electric power.

In another aspect, this invention is directed to a charging stationwhich can transmit electric power to first and second vehicles in anon-contact manner, and the charging station includes a plurality ofelectric power transmission portions which can transmit electric powerto the vehicles in a non-contact manner and an electric powertransmission control unit controlling electric power transmission fromthe plurality of electric power transmission portions. The electricpower transmission control unit has a first electric power transmissionportion which is not transmitting electric power of the plurality ofelectric power transmission portions transmit weak electric power whenthe electric power transmission control unit receives a signalrequesting electric power transmission from the first vehicle. Thesecond vehicle transmits to the electric power transmission controlunit, an occupation signal which allows determination that a parkingposition corresponds to the first electric power transmission portionwhen the second vehicle is parked at a position where the second vehiclecan receive electric power from the first electric power transmissionportion and when the second vehicle receives weak electric power fromthe first electric power transmission portion. The electric powertransmission control unit guides the first vehicle to an electric powertransmission portion other than the first electric power transmissionportion when the electric power transmission control unit receives theoccupation signal from the second vehicle.

According to the configuration above, for example, even when the secondvehicle remains stopped without moving after charging by the firstelectric power transmission portion, the charging station is notified ofthe fact that the second vehicle is occupying the first electric powertransmission portion. Therefore, the charging station can guide thefirst vehicle, which has sent a signal requesting electric powertransmission, to an electric power transmission portion other than thefirst electric power transmission portion.

In another aspect, this invention is directed to a vehicle including anelectric power reception device which can receive electric power from acharging station in a non-contact manner, a power storage device, acharging relay provided between the electric power reception device andthe power storage device, a distance sensing portion, and an electricpower reception control unit controlling the charging relay and thedistance sensing portion. The distance sensing portion has a resistorand a distance sensing relay with which the resistor is connectedbetween a pair of output lines of the electric power reception device.The electric power reception control unit renders the charging relayconductive and renders the distance sensing relay non-conductive whenthe power storage device is charged, and renders the charging relaynon-conductive and renders the distance sensing relay conductive aftercharging of the power storage device is completed.

With the configuration above, reception of weak electric power by thevehicle can be separate from charging of the power storage device and adistance can suitably be sensed based on a received voltage generated bythe weak electric power.

According to the present invention, a vehicle which has newly arrived ata charging station can be guided to an empty electric power transmissionportion, with an electric power transmission portion where anothervehicle has already parked being avoided.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a non-contact electricpower transmission system representing one example of an embodiment ofthe present invention.

FIG. 2 is a diagram for illustrating parking of a (first) vehicle at aparking position within a charging station.

FIG. 3 is a diagram for illustrating parking of a (second) vehicle at aparking position within the charging station.

FIG. 4 is a flowchart for illustrating overview of processing performedby vehicle 10A or 10B and a charging station 90 in non-contact electricpower transmission.

FIG. 5 is a flowchart for illustrating details of processing forselecting an electric power transmission coil performed in step S540 inFIG. 4.

FIG. 6 is a timing chart representing variation in transmission electricpower and a received voltage which are varied during the course of theprocessing in FIGS. 4 and 5.

FIG. 7 is a diagram for illustrating a modification of occupationchecking processing or pairing processing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described hereinafter indetail with reference to the drawings. The same or correspondingelements in the drawings have the same reference characters allotted anddescription thereof will not be repeated.

(Description of Overview of Non-Contact Electric Power TransmissionSystem)

FIG. 1 is an overall configuration diagram of a non-contact electricpower transmission system representing one example of an embodiment ofthe present invention. FIGS. 2 and 3 are diagrams for illustratingparking of vehicles at parking positions within a charging station.Initially, overview of the present embodiment will be described withreference to FIGS. 1 to 3.

Referring to FIG. 1, a non-contact electric power transmission system inthe present embodiment includes vehicles 10A and 10B and a chargingstation 90. Charging station 90 includes a plurality of electric powertransmission portions 700A and 700B which can transmit electric power tothe vehicles in a non-contact manner and an electric power transmissioncontrol unit (a power supply ECU 800) controlling electric powertransmission from the plurality of electric power transmission portions700A and 700B.

As shown in FIG. 2, a case that vehicle 10B which has arrived earlier isparked over electric power transmission portion 700B for charging isconsidered. Vehicle 10B uses weak electric power from electric powertransmission portion 700B as a test signal for positioning. To that end,vehicle 10B transmits a signal for requesting electric powertransmission to the charging station. When the charging station receivesthe signal for requesting electric power transmission, it has anelectric power transmission portion which is not transmitting electricpower of the plurality of electric power transmission portions 700A and700B transmit weak electric power. In the case of FIG. 2, a vehicle hasbeen parked at neither of the plurality of electric power transmissionportions 700A and 700B and neither of electric power transmissionportions 700A and 700B has been transmitting electric power. Therefore,both of electric power transmission portions 700A and 700B transmit weakelectric power. Vehicle 10B selects electric power transmission portion700B, and as vehicle 10B approaches electric power transmission portion700B, an electric power reception portion 100 starts to detect weakelectric power. Therefore, positioning is carried out based on intensityof weak electric power (a received voltage VR).

Here, as shown in FIG. 3, a case that vehicle 10B has not yet moved fromelectric power transmission portion 700B in spite of completion ofcharging of vehicle 10B is considered. As shown in FIG. 3, power supplyECU 800 has an electric power transmission portion which is nottransmitting electric power of the plurality of electric powertransmission portions 700A and 700B transmit weak electric power whenpower supply ECU 800 receives a signal requesting electric powertransmission from vehicle 10A. For example, when charging of vehicle 10Bby electric power transmission portion 700B has been completed, both ofthe plurality of electric power transmission portions 700A and 700Btransmit weak electric power.

When vehicle 10B is parked at a position where it can receive electricpower from electric power transmission portion 700B and when vehicle 10Breceives weak electric power from electric power transmission portion700B, vehicle 10B transmits to power supply ECU 800, an occupationsignal which allows determination that the parking position correspondsto electric power transmission portion 700B. Transmission is carried outthrough a communication portion 510 and a communication portion 810 inFIG. 1. Power supply ECU 800 stops transmission of weak electric powerfrom electric power transmission portion 700B when it receives theoccupation signal of electric power transmission portion 700B fromvehicle 10B, and guides vehicle 10A to an electric power transmissionportion other than electric power transmission portion 700B, that is, toelectric power transmission portion 700A in the case of FIG. 3.

With the configuration above, for example, even when vehicle 10B remainsstopped without moving after charging by electric power transmissionportion 700B, charging station 90 is notified of the fact that vehicle10B is occupying electric power transmission portion 700B. Therefore,charging station 90 can guide vehicle 10A, which has sent a signalrequesting electric power transmission, to an electric powertransmission portion other than electric power transmission portion 700B(electric power transmission portion 700A in FIG. 3).

Preferably, power supply ECU 800 allows electric power transmission withelectric power characteristics of weak electric power from the pluralityof electric power transmission portions 700A and 700B being differed foreach electric power transmission portion. Vehicle 10B transmits to powersupply ECU 800, an occupation signal of electric power transmissionportion 700B in accordance with electric power characteristics ofreceived weak electric power.

According to such a configuration, vehicle 10B can know based onelectric power characteristics of the received weak electric power, whatkind of electric power transmission portion the electric powertransmission portion where vehicle 10B is stopped is. Then, vehicle 10Bcan return information which allows determination of an electric powertransmission portion to charging station 90.

More preferably, electric power characteristics differed for eachelectric power transmission portion are a time period for supply (TA, TBin FIG. 6) of weak electric power, and vehicle 10B transmits a signalindicating a time period for supply (TB in FIG. 6) as an occupationsignal of electric power transmission portion 700B.

More preferably, electric power characteristics differed for eachelectric power transmission portion are the number of times of switchingbetween on and off of weak electric power (see FIG. 7), and vehicle 10Btransmits a signal indicating the number of switching as an occupationsignal of electric power transmission portion 700B.

Without electric power transmission with characteristics of weakelectric power being differed for each electric power transmissionportion, if vehicle 10B holds, also after end of charging, informationat the time when pairing of vehicle 10B is carried out before chargingto determine an electric power transmission portion, informationallowing determination of the electric power transmission portion inresponse to transmission of the same weak electric power by all electricpower transmission portions or reception of communication fromcommunication portion 810 may be returned to charging station 90.

Namely, preferably, vehicle 10B is configured to hold informationindicating that an electric power transmission portion used for chargingis electric power transmission portion 700B of the plurality of electricpower transmission portions, also after end of charging. Then, whenvehicle 10B receives weak electric power while it is parked at aposition corresponding to electric power transmission portion 700B (aparking position B in FIG. 2) after end of charging, vehicle 10Btransmits an occupation signal based on the held information.

Preferably, each of vehicles 10A and 10B includes an electric powerreception device 120 which can receive electric power from any of theplurality of electric power transmission portions, a power storagedevice 300, a charging relay 210 provided between electric powerreception device 120 and power storage device 300, a distance sensingportion 204, and an electric power reception control unit (a vehicle ECU500) controlling charging relay 210 and distance sensing portion 204.Distance sensing portion 204 has a resistor 201 and a distance sensingrelay 202 with which resistor 201 is connected between a pair of outputlines of electric power reception device 120. Vehicle ECU 500 renderscharging relay 210 conductive and renders distance sensing relay 202non-conductive when power storage device 300 is charged, and renderscharging relay 210 non-conductive and renders distance sensing relay 202conductive after completion of charging of power storage device 300.

According to the configuration above, reception of weak electric powerby a vehicle can be separate from charging of power storage device 300,and a distance can suitably be sensed based on received voltage VRgenerated by weak electric power.

Details of each feature in the non-contact electric power transmissionsystem will now further be described.

(Detailed Configuration of Non-Contact Electric Power TransmissionSystem)

Referring to FIG. 1, the non-contact electric power transmission systemin the present embodiment is constituted of vehicles 10A and 10B onwhich electric power reception device 120 configured to be able toreceive electric power in a non-contact manner is mounted and chargingstation 90 including electric power transmission devices 20A and 20Btransmitting electric power from the outside of the vehicle to electricpower reception portion 100.

Vehicle 10A includes electric power reception device 120, power storagedevice 300, a motive power generation apparatus 400, communicationportion 510, vehicle ECU 500, and a display portion 520. Electric powerreception device 120 includes electric power reception portion 100, afilter circuit 150, and a rectification portion 200. Vehicle 10B is alsoconfigured similarly to vehicle 10A, although the inside is notillustrated.

Charging station 90 includes an external power supply 900, electricpower transmission devices 20A and 20B, communication portion 810, andpower supply ECU 800. Electric power transmission devices 20A and 20Binclude power supply portions 600A and 600B, filter circuits 610A and610B, and electric power transmission portions 700A and 700B,respectively.

For example, as shown in FIG. 2, electric power transmission devices 20Aand 20B are provided on or in the ground at parking positions A and B,respectively, and electric power reception device 120 is arranged in alower portion of a vehicle body. A location of arrangement of electricpower reception device 120 is not limited as such. For example, whenelectric power transmission devices 20A and 20B are provided above orlateral to vehicle 10, electric power reception device 120 may beprovided in an upper portion of the vehicle body or in a peripheralsurface to front surface, a rear surface, and a side surface) of thevehicle body.

Electric power reception portion 100 includes a secondary coil forreceiving in a non-contact manner, (AC) electric power output from anyof electric power transmission portions 700A and 700B of electric powertransmission devices 20A and 20B. Electric power reception portion 100outputs received electric power to rectification portion 200.Rectification portion 200 rectifies AC power received by electric powerreception portion 100 and outputs the AC power to power storage device300. Filter circuit 150 is provided between electric power receptionportion 100 and rectification portion 200 and suppresses harmonic noisegenerated during electric power reception from any of electric powertransmission portions 700A and 700B. Filter circuit 150 is formed, forexample, from an LC filter including an inductor and a capacitor.

Power storage device 300 is a rechargeable DC power supply and it isimplemented, for example, by such a secondary battery as a lithium ionbattery or a nickel metal hydride battery. A voltage of power storagedevice 300 is, for example, around 200 V. Power storage device 300stores not only electric power output form rectification portion 200 butalso electric power generated by motive power generation apparatus 400.Then, power storage device 300 supplies the stored electric power tomotive power generation apparatus 400. A large-capacity capacitor canalso be adopted as power storage device 300. Though not particularlyillustrated, a DC-DC converter regulating an output voltage fromrectification portion 200 may be provided between rectification portion200 and power storage device 300.

Motive power generation apparatus 400 generates driving force forrunning of vehicle 10A by using electric power stored in power storagedevice 300. Though not particularly illustrated, motive power generationapparatus 400 includes, for example, an inverter receiving electricpower from power storage device 300, a motor driven by the inverter, anddrive wheels driven by the motor. Motive power generation apparatus 400may include a generator for charging power storage device 300 and anengine which can drive the generator.

Vehicle ECU 500 includes a central processing unit (CPU), a storagedevice, and an input/output buffer (none of which is shown), receivesinput of signals from various sensors and outputs control signals toeach device, and controls each device in vehicle 10A. By way of example,vehicle ECU 500 controls running of vehicle 10A and charging of powerstorage device 300. Such control is not limited to processing bysoftware and processing with dedicated hardware (electronic circuitry)can also be performed.

Relay 210 is provided between rectification portion 200 and powerstorage device 300. Relay 210 is turned on by vehicle ECU 500 duringcharging of power storage device 300 by electric power transmissiondevices 20A and 20B. A system main relay (SMR) 310 is provided betweenpower storage device 300 and motive power generation apparatus 400. SMR310 is turned on by vehicle ECU 500 when start-up of motive powergeneration apparatus 400 is requested.

Relay 202 is provided between rectification portion 200 and relay 210. Avoltage VR across opposing ends of resistor 201 connected in series withrelay 202 is detected by a voltage sensor 203, and sent to vehicle ECU500.

Vehicle ECU 500 communicates with communication portion 810 of chargingstation 90 through communication portion 510 during charging of powerstorage device 300 by electric power transmission devices 20A and 20B,and exchanges with power supply ECU 800, information on start/stop ofcharging or an electric power reception condition of vehicle 10A.

Referring to FIGS. 1 and 2, vehicle 10A or charging station 90determines whether or not the secondary coil within electric powerreception device 120 is positioned with respect to a primary coil withinelectric power transmission device 20A based on a not-shown car-mountedcamera or on intensity of received electric power during test electricpower transmission (transmission of weak electric power) by electricpower transmission portion 700A, and a user is notified of a resultthrough display portion 520. The user moves vehicle 10A such thatpositional relation between electric power reception device 120 andelectric power transmission device 20A is good for electric powertransmission and reception based on information obtained from displayportion 520. The user does not necessarily have to operate a steeringwheel or an accelerator, and vehicle 10A may automatically move forpositioning while the user monitors such an operation on display portion520.

In test electric power transmission with weak electric power, output tosuch an extent as being used in what is called a specified low powerradio station (equal to or lower than 1/100 of full-scale electric powertransmission used for charging) is preferred.

Referring again to FIG. 1, power supply portions 600A and 600B receiveelectric power from external power supply 900 such as a commercialsystem power supply and generate AC power having a prescribedtransmission frequency.

Electric power transmission portions 700A and 700B each include aprimary coil for non-contact electric power transmission to electricpower reception portion 100. Electric power transmission portions 700Aand 700B each receive AC power having a transmission frequency frompower supply portions 600A and 600B and transmits electric power toelectric power reception portion 100 of vehicle 10A in a non-contactmanner through electromagnetic field generated around electric powertransmission portions 700A and 700B.

Filter circuits 610A and 610B are provided between power supply portions600A and 600B and electric power transmission portions 700.A and 700B,respectively, and suppress harmonic noise generated from power supplyportions 600A and 600B. Filter circuits 610A and 610B are each formedfrom an LC filter including an inductor and a capacitor.

Power supply ECU 800 includes a CPU, a storage device, and aninput/output buffer (none of which is shown), receives input of signalsfrom various sensors and outputs control signals to each device, andcontrols each device in charging station 90. By way of example, powersupply ECU 800 controls switching of power supply portions 600A and 600Bsuch that power supply portions 600A and 600B generate AC power having atransmission frequency. Such control is not limited to processing bysoftware and processing with dedicated hardware (electronic circuitry)can also be performed.

Power supply ECU 800 communicates with communication portion 510 ofvehicle 10A through communication portion 810 during electric powertransmission to vehicle 10A, and exchanges with vehicle 10A, informationon start/stop of charging or an electric power reception condition ofvehicle 10A.

AC power having a prescribed transmission frequency is supplied, frompower supply portions 600A and 600B to electric power transmissionportions 700A and 700B through filter circuits 610A and 610B. Each ofelectric power transmission portions 700A and 700B and electric powerreception portion 100 of vehicle 10A includes a coil and a capacitor,and is designed to resonate at the transmission frequency. A Q valuerepresenting resonance intensity of electric power transmission portions700A and 700B and electric power reception portion 100 is preferably 100or higher.

When AC power is supplied from power supply portions 600A and 600B toelectric power transmission portions 700A and 700B through filtercircuits 610A and 610B, energy (electric power) is transferred from anyof electric power transmission portions 700A and 700B to electric powerreception portion 100 through electromagnetic field formed between theprimary coil included in any of electric power transmission portions700A and 700B and the secondary coil of electric power reception portion100. Then, energy (electric power) transferred to electric powerreception portion 100 is supplied to power storage device 300 throughfilter circuit 150 and rectification portion 200.

Though not particularly illustrated, in electric power transmissiondevices 20A and 20B, an insulating transformer may be provided betweenelectric power transmission portions 700A and 700B and power supplyportions 600A and 600B (for example, between electric power transmissionportions 700A and 700B and filter circuits 610A and 610B). In vehicle10A as well, an insulating transformer may be provided between electricpower reception portion 100 and rectification portion 200 (for example,between electric power reception portion 100 and filter circuit 150).

(Procedure of Non-Contact Electric Power Transmission)

FIG. 4 is a flowchart for illustrating overview of processing performedby vehicle 10A or 10B and charging station 90 in non-contact electricpower transmission.

Referring to FIGS. 1 and 4, in the vehicle, whether or not a non-contactcharging switch designating whether or not to carry out non-contactcharging is ON is determined in step S10. Though not particularlylimited, preferably, the non-contact charging switch has automaticallybeen set to ON while the vehicle is started up and the vehicle isconfigured such that the user can switch setting to OFF.

In step S510, power supply ECU 800 of charging station 90 broadcasts asignal notifying that a situation allows charging when there is an emptyparking position.

When vehicle ECU 500 of vehicle 10A receives this signal in step S20,the process proceeds to step S30, and vehicle ECU 500 transmits arequest for transmission of weak electric power to charging station 90.

In step S530, power supply ECU 800 of charging station 90 receives therequest for electric power transmission.

When charging station 90 receives in step S530 the request for electricpower transmission from the vehicle, in response thereto, the chargingstation performs processing for selecting an electric power transmissioncoil in step S540.

FIG. 5 is a flowchart for illustrating details of processing forselecting an electric power transmission coil performed in step S540 inFIG. 4. The processing in this flowchart is performed by power supplyECU 800 of charging station 90. Referring to FIGS. 1 and 5, initially instep S701, whether or not electric power transmission portion 700A istransmitting electric power is determined. When electric powertransmission portion 700A is transmitting electric power in step S701,the process proceeds to step S702, and when electric power transmissionportion 700A is not transmitting electric power, the process proceeds tostep S703.

Whether or not electric power transmission portion 700B is transmittingelectric power is determined in step S702. When electric powertransmission portion 700B is transmitting electric power in step S702,the process proceeds to step S712, and when electric power transmissionportion 700B is not transmitting electric power, the process proceeds tostep S704.

Whether or not electric power transmission portion 700B is transmittingelectric power is determined in step S703. When electric powertransmission portion 700B is transmitting electric power in step S703,the process proceeds to step S705, and when electric power transmissionportion 700B is not transmitting electric power, the process proceeds tostep S706.

When the process proceeds to step S704, power supply ECU 800 selectselectric power transmission portion 700B as an electric powertransmission candidate. When the process proceeds to step S705, powersupply ECU 800 selects electric power transmission portion 700A as anelectric power transmission candidate. When the process proceeds to stepS706, power supply ECU 800 selects electric power transmission portions700A and 700B as electric power transmission candidates.

When an electric power transmission candidate is determined in any ofsteps S704 to S706, the selected electric power transmission portiontransmits weak electric power in step S707. In this transmission of weakelectric power, a test signal for checking whether any electric powertransmission portion is occupied by another vehicle is used. Forexample, as shown in FIG. 3, when vehicle 10A requests transmission ofweak electric power for positioning for charging while vehicle 10B whichhas completed charging is occupying electric power transmission portion700B, both of electric power transmission portions 700A and 700Btransmit weak electric power.

Here, vehicle 10B can immediately receive weak electric power fromelectric power transmission portion 700B. Vehicle 10B corresponds to“another vehicle” in step S708. Vehicle 10B stands by in such a statethat it can receive weak electric power from electric power transmissionportion 700B even when charging thereof has been completed. Then, whenvehicle 10B receives weak electric power from electric powertransmission portion 700B, vehicle 10B transmits a signal informing thatit is occupying electric power transmission portion 700B to power supplyECU 800 of charging station 90. When vehicle 10B is occupying electricpower transmission portion 700A, vehicle 10B transmits a signalinforming that it is occupying electric power transmission portion 700B(an occupation signal) to power supply ECU 800.

In step S708, vehicle ECU 800 checks contents of the occupation signalreceived from another vehicle (a vehicle other than the vehicle whichhas requested transmission of weak electric power for charging) which isparked.

Though an example in which a vehicle receives weak electric power andreturns an occupation signal to charging station 90 has been shown inthe present embodiment, charging station 90 may detect whether or noteach electric power transmission portion is occupied after weak electricpower is transmitted. For example, when a vehicle is present at aposition where it can receive electric power, effective electric poweron the transmission side increases. Therefore, effective electric powerduring transmission of weak electric power may be detected by a currentsensor and a voltage sensor provided in each electric power transmissionportion and an occupation signal of the occupied electric powertransmission portion may be generated in the charging station.

In succession, whether electric power transmission portion 700A isoccupied or is transmitting electric power is determined in step S709.When electric power transmission portion 700A is occupied or istransmitting electric power in step S709, the process proceeds to stepS710, and when electric power transmission portion 700A is not occupiednor is transmitting electric power, the process proceeds to step S711.

Whether electric power transmission portion 700B is occupied or istransmitting electric power is determined in step S710. When electricpower transmission portion 700B is occupied or is transmitting electricpower in step S710, the process proceeds to step S712, and when electricpower transmission portion 700B is not occupied nor is transmittingelectric power, the process proceeds to step S713.

Whether electric power transmission portion 700B is occupied or istransmitting electric power is determined in step S711. When electricpower transmission portion 700B is occupied or is transmitting electricpower in step S711, the process proceeds to step S714, and when electricpower transmission portion 700B is not occupied nor is transmittingelectric power, the process proceeds to step S715.

Through the selection processing above, the processing is allocated toany of steps S712 to S715. When the process proceeds to step S712, everyelectric power transmission portion is transmitting electric power or isoccupied, and hence a request for positioning from a vehicle which hasnewly come to charging station 90 is rejected. When the process proceedsto step S713, electric power transmission portion 700B is selected as asubject of transmission of weak electric power for positioning. When theprocess proceeds to step S714, electric power transmission portion 700Ais selected as a subject of transmission of weak electric power forpositioning. When the process proceeds to step S715, electric powertransmission portions 700A and 700B are selected as subjects oftransmission of weak electric power for positioning.

When processing in any of steps S712 to S715 is completed, the processproceeds to step S716 and control returns to the flowchart in FIG. 4.

FIG. 6 is a timing chart representing variation in transmission electricpower and a received voltage which are varied during the course of theprocessing in FIGS. 4 and 5.

FIG. 6 shows an operation waveform in a case that vehicle 10A hasrequested transmission of weak electric power for positioning whilevehicle 10B is occupying electric power transmission portion 700B aftercompletion of charging (while electric power transmission portion 700Bis not transmitting electric power) as exemplified in FIG. 3.

In response to a request for transmission of weak electric power fromvehicle 10A (step S30 in FIG. 4), at time ti, weak electric power istransmitted from electric power transmission portion 700A of electricpower transmission device 20A and electric power transmission portion700B of electric power transmission device 20B.

Preferably, weak electric power here is transmitted with electric powercharacteristics being different for each electric power transmissionportion. Differing electric power characteristics for each electricpower transmission portion is exemplified by differing a time period forsupply of transmission electric power, such as a time period for supplyTA from electric power transmission portion 700A and a time period forsupply TB from electric power transmission portion 700B. Another exampleof differing electric power characteristics for each electric powertransmission portion may be electric power transmission with the numberof times of on and off being differed for each electric powertransmission portion as shown in FIG. 7.

In the example shown in FIG. 6, from time t1 to t2, vehicle 10B receivesweak electric power for time period of supply TB from electric powertransmission portion 700B. When vehicle 10B returns a signal indicatingtime period for supply TB to the charging station, the charging stationrecognizes that electric power transmission portion 700B correspondingto time period for supply TB is occupied. Vehicle 10B may recognize thatelectric power is transmitted from electric power transmission portion700B and return a signal indicating occupation of electric powertransmission portion 700B.

From time t11, electric power transmission portion 700B is excluded fromelectric power transmission portions to which vehicle 10A can be guided,and positioning with electric power transmission portion 700A is carriedout.

Referring again to FIG. 4, when the processing for selecting a coil instep S540 is completed, charging station 90 transmits in step S550, weakelectric power for positioning between an electric power transmissiondevice including the selected electric power transmission portion andelectric power reception device 120. In the waveform example in FIG. 6,since electric power transmission device 20B is occupied by vehicle 10Bwhich has arrived earlier, weak electric power is transmitted only fromelectric power transmission device 20A.

In step S50, vehicle 10A carries out positioning through automatic ormanual movement of vehicle 10A (see a time point t11 in FIG. 6). Duringpositioning, vehicle ECU 500 renders relay 202 conductive and obtainsmagnitude of received voltage VR which is produced across the opposingends of resistor 201 and detected by voltage sensor 203. Since thisvoltage is lower than a voltage in full-scale electric powertransmission, vehicle ECU 500 sets relay 210 to of so as not to beaffected by power storage device 300 during detection.

In the vehicle, vehicle ECU 500 notifies in step S60 the fact thatmagnitude of received voltage VR has exceeded a threshold value THthrough display portion 520. The user thus recognizes that positioninghas been successful. Thereafter, when the user gives a notification thatthe parking position is OK by pressing a parking switch within vehicle10A, the process proceeds to step S70 (see a time point t12 in FIG. 6).

In step S70, vehicle ECU 500 transmits a request for stoppingtransmission of weak electric power for positioning to charging station90. In step S570, power supply ECU 800 of charging station 90 receivesthe request for stopping transmission of weak electric power, andtransmission of weak electric power for positioning by electric powertransmission devices 20A and 20B ends (see a time point t13 in FIG. 6).

In step S80 and step S580, vehicle ECU 500 and power supply ECU 800perform pairing processing for checking whether or not positioning withany of electric power transmission devices 20A and 20B has reliably beenachieved.

As shown with time from t14 to t15 in FIG. 6, when electric powertransmission device 20A is selected as a subject of electric powertransmission in step S540, power supply ECU 800 allows test electricpower transmission for pairing from electric power transmission portion700A of electric power transmission device 20A.

In contrast, when electric power transmission device 20B is selected asa subject of electric power transmission in step S540, power supply ECU800 allows test electric power transmission for pairing from electricpower transmission portion 700B of electric power transmission device20B.

In test electric power transmission used in the pairing processing, asin positioning, output to such an extent as being used in what is calleda specified low power radio station (equal to or lower than 1/100 offull-scale electric power transmission used for charging) is preferred.

In FIG. 6, power supply ECU 800 differs a duration of on of transmissionelectric power for each electric power transmission device. Namely, intransmission of electric power by electric power transmission device20A, electric power transmission is carried out with transmissionelectric power being turned on for a time period of TA (see a time pointt14 in FIG. 6). When vehicle 10B has not occupied electric powertransmission device 20B, as shown with a dashed line, electric powertransmission device 20B also transmits electric power with transmissionelectric power being turned on for time period of TB (see time pointst14 to t16 in FIG. 6).

In steps S90 and S100, vehicle ECU 500 counts the duration of on ofreceived electric power, and in step S110, notifies power supply ECU 800of the counted duration of on. In the example in FIG. 6, electric powerreception device 120 receives transmission electric power from electricpower transmission device 20A. Vehicle ECU 500 notifies power supply ECU800 of the fact that the duration of on of received electric power isTA. Power supply ECU 800 can thus reliably confirm positioning ofvehicle 10A with electric power transmission device 20A.

In step S620, charging station 90 performs processing for full-scaleelectric power transmission from the electric power transmission devicewhich is in positioning and has completed checking that a subject hasbeen determined through pairing (see a time point t17 in FIG. 6). In theexample in FIG. 6, electric power transmission device 20A performsprocessing for electric power transmission. In step S120, vehicle 10Aperforms processing for full-scale electric power reception by electricpower reception device 120 and power storage device 300 is charged withreceived electric power. Then, when charging of power storage device 300is completed, processing on the vehicle side and in the charging stationends.

An example in which electric power transmission with characteristics ofweak electric power being differed for each electric power transmissionportion is carried out from t1 to t2 in FIG. 6 has been shown. Withoutelectric power transmission with characteristics of weak electric powerbeing differed for each electric power transmission portion, if vehicle10B holds, also after end of charging, information at the time whenpairing of vehicle 10B is carried out before charging to determine anelectric power transmission portion, information allowing determinationof an electric power transmission portion may be returned to chargingstation 90 in response to transmission of the same weak electric powerby all electric power transmission portions or reception ofcommunication from communication portion 810.

(Modification of Occupation Checking Processing and Pairing)

FIG. 7 is a diagram for illustrating a modification of occupationchecking processing or pairing processing. In FIG. 7, power supply ECU800 differs a cycle of switching between on and off of transmissionelectric power for each electric power transmission device. Namely,electric power transmission device 20A switches between on and off oftransmission electric power every cycle ΔTA and electric powertransmission device 20B switches between on and off of transmissionelectric power every cycle ΔTB.

Vehicle ECU 500 notifies power supply ECU 800 of the number of times ofswitching between on and off of received electric power. In the examplein FIG. 7, vehicle. ECU 500 counts the number of times of occurrence ofswitching between on and off from time t20 to t21 and notifies powersupply ECU 800 of the count. Power supply ECU 800 thus knows whichelectric power transmission device is occupied by the vehicle or withwhich electric power transmission device the vehicle is in positioning.

In the modification in FIG. 7, processing for checking occupation orpairing is achieved, with the use of transmission electric power,however, limitation thereto is not intended. Pairing can be achievedwith various techniques, and for example, pairing may be achieved byproviding a radio frequency identification (RFID) tag and an RFID readerin a vehicle and an electric power transmission portion, respectively,based on an RFID technique.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

What is claimed is:
 1. A non-contact electric power transmission system,comprising: first and second vehicles; and a charging station, saidcharging station including a plurality of electric power transmissionportions which can transmit electric power to the vehicles in anon-contact manner, and an electric power transmission control unitcontrolling electric power transmission from said plurality of electricpower transmission portions, said electric power transmission controlunit having a first electric power transmission portion, which is nottransmitting electric power, of said plurality of electric powertransmission portions transmit weak electric power when said electricpower transmission control unit receives a signal requesting electricpower transmission from said first vehicle, said second vehicletransmitting to said electric power transmission control unit, anoccupation signal which allows determination that a parking positioncorresponds to said first electric power transmission portion when saidsecond vehicle is parked at a position where the second vehicle canreceive electric power from said first electric power transmissionportion and when said second vehicle receives weak electric power fromsaid first electric power transmission portion, and said electric powertransmission control unit guiding said first vehicle to an electricpower transmission portion different from said first electric powertransmission portion when the electric power transmission control unitreceives said occupation signal from said second vehicle.
 2. Thenon-contact electric power transmission system according to claim 1,wherein said electric power transmission control unit allows electricpower transmission with electric power characteristics of weak electricpower from said plurality of electric power transmission portions beingdiffered for each electric power transmission portion, and said secondvehicle transmits to said electric power transmission control unit, saidoccupation signal in accordance with the electric power characteristicsof received weak electric power.
 3. The non-contact electric powertransmission system according to claim 2, wherein said electric powercharacteristics differed for each electric power transmission portionare a time period for supply of said weak electric power, and saidsecond vehicle transmits a signal indicating said time period for supplyas said occupation signal.
 4. The non-contact electric powertransmission system according to claim 2, wherein said electric powercharacteristics differed for each electric power transmission portionare the number of times of switching between on and off of said weakelectric power, and said second vehicle transmits a signal indicatingsaid number of times of switching as said occupation signal.
 5. Thenon-contact electric power transmission system according to claim 1,wherein said second vehicle holds information indicating that theelectric power transmission portion used for charging is said firstelectric power transmission portion of said plurality of electric powertransmission portions, also after end of charging, and said secondvehicle transmits said occupation signal based on said information whenthe second vehicle receives said weak electric power while the secondvehicle is parked at the position corresponding to said first electricpower transmission portion after end of charging.
 6. The non-contactelectric power transmission system according to claim 1, wherein. saidsecond vehicle includes an electric power reception device which canreceive electric power from any of said plurality of electric powertransmission portions, a power storage device, a charging relay providedbetween said electric power reception device and said power storagedevice, a distance sensing portion, and an electric power receptioncontrol unit controlling said charging relay and said distance sensingportion, said distance sensing portion has a resistor, and a distancesensing relay with which said resistor is connected between a pair ofoutput lines of said electric power reception device, and said electricpower reception control unit renders said charging relay conductive andrenders said distance sensing relay non-conductive when said powerstorage device is charged, and renders said charging relaynon-conductive and renders said distance sensing relay conductive aftercharging of said power storage device is completed.
 7. A chargingstation which can transmit electric power to first and second vehiclesin a non-contact manner, comprising: a plurality of electric powertransmission portions which can transmit electric power to the vehiclesin a non-contact manner; and an electric power transmission control unitcontrolling electric power transmission from said plurality of electricpower transmission portions, said electric power transmission controlunit having a first electric power transmission portion which is nottransmitting electric power of said plurality of electric powertransmission portions transmit weak electric power when said electricpower transmission control unit receives a signal requesting electricpower transmission from said first vehicle, said second vehicletransmitting to said electric power transmission control unit, anoccupation signal which allows determination that a parking positioncorresponds to said first electric power transmission portion when saidsecond vehicle is parked at a position where the second vehicle canreceive electric power from said first electric power transmissionportion and when said second vehicle receives weak electric power fromsaid first electric power transmission portion, and said electric powertransmission control unit guiding said first vehicle to an electricpower transmission portion other than said first electric powertransmission portion when the electric power transmission control unitreceives said occupation signal from said second vehicle.
 8. A vehicle,comprising: an electric power reception device which can receiveelectric power from a charging station in a non-contact manner; a powerstorage device; a charging relay provided between said electric powerreception device and said power storage device; a distance sensingportion; and an electric power reception control unit controlling saidcharging relay and said distance sensing portion, said distance sensingportion having a resistor, and a distance sensing relay with which saidresistor is connected between a pair of output lines of said electricpower reception device, and said electric power reception control unitrendering said charging relay conductive and rendering said distancesensing relay non-conductive when said power storage device is charged,and rendering said charging relay non-conductive and rendering saiddistance sensing relay conductive after charging of said power storagedevice is completed.